Thermoplastic vulcanizates from a polyolefin and either EPDM rubber or butyl rubber are commercially available. These compositions are very desirable due to their ability to be processed in conventional thermoplastic shaping and forming equipment while still exhibiting some of the properties of crosslinked rubbers. The hardness (e.g., Shore A/D or 100 percent modulus) can be adjusted by varying the ratio of thermoplastic polyolefin to rubber. Achieving desirable physical properties in a thermoplastic vulcanizate are at least partially dependent upon achieving a suitable dispersion or interdispersion of the polyolefin with the rubber. The correlation between physical properties and dispersibility has limited thermoplastic vulcanizates to two or more polymers that inherently have or can be modified to have dispersibility or interdispersibility of a suitable nature. Thermoplastic vulcanizates from a poly(.alpha.-olefin) and EPDM or butyl rubber, being hydrocarbon-based, swell in hydrocarbon oils. This has excluded their use in some applications where extensive exposure to hydrocarbon oils occurs.
Blends of polypropylene with elastic copolymers of alpha-olefin/cyclic olefin are described in U.S. Pat. Nos. 5,723,545 and 5,763,532. These applications claim priority from the same U.S. application as does WO 94/7113.